FINAL ASSESSMENT/EXAMINATION JULY 2015 PLEASE READ ALL INSTRUCTIONS CAREFULLY BEFORE YOU BEGIN THIS EXAMINATION

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1 THE UNIVERSITY OF TRINIDAD & TOBAGO FINAL ASSESSMENT/EXAMINATION JULY 2015 Course Code and Title: CNET 2001 Network Architecture Programme: B.A.Sc. ICT Computer Engineering Date: Tuesday July 28, 2015 Time: 9:00 a.m. 12:00 noon Duration: 3 Hours PLEASE READ ALL INSTRUCTIONS CAREFULLY BEFORE YOU BEGIN THIS EXAMINATION Instructions to Candidates 1. This paper has 8 pages and 7 questions. 2. Calculators are allowed, though not necessary. 3. The total marks for this paper is You are required to return the question paper with your answer script. Key Examination Protocol 1. Students please note that academic dishonesty (or cheating) includes but is not limited to plagiarism, collusion, falsification, replication, taking unauthorised notes or devices into an examination, obtaining an unauthorised copy of the examination paper, communicating or trying to communicate with another candidate during the examination, and being a party to impersonation in relation to an examination. 2. The above mentioned and any other actions which compromise the integrity of the academic evaluation process will be fully investigated and addressed in accordance with UTT s academic regulations. 3. Please be reminded that speaking without the Invigilator s permission is NOT allowed. Page 1 of 8

2 Question 1 Many network devices work together to transport data across the network, such as bridges, switches, routers among others. a. What is a bridge? b. What ability of a bridge enables it to connect different types of Ethernet? c. At what layer does a switch traditionally operate? d. i. What kind of connection is used to attach a host to a switch? ii. What advantage does this bring? e. What are the main advantages of using a switch over a bridge? f. There are two broad categories of MAC protocols. These are deterministic and non-deterministic. i. Explain what is meant by a deterministic MAC protocol, giving one example. ii. Explain what is meant by a non-deterministic MAC protocol, giving one example. Page 2 of 8

3 2. An network administrator has done an analysis for his organisation s planned network and found the number and grouping of required hosts to be as follows: Marketing LAN Staff Computers: 40 Router (LAN Gateway): 1 Switches (management): 4 Total for Marketing subnetwork: 49 Shipping LAN Staff Computers: 10 Router (LAN Gateway): 1 Switches (management): 1 Total for Shipping subnetwork: 12 WAN Router - Router WAN: 2 Total for WAN: 2 Purchasing LAN Staff Computers: 6 Router (LAN Gateway): 1 Switches (management): 1 Total for Purchasing subnetwork: 8 HR LAN Administrator Computers: 8 Server: 1 Router (LAN Gateway): 1 Switch (management): 1 Total for HR subnetwork: 11 As an administrator you are assigned an address block of /25 as a whole. Using VLSM, you are required to assign addresses to each subnetwork. Answer the following questions in your answer booklet. Make sure to show your working. a. What is the network address that you assign to each subnetwork in binary format? b. What is the first usable network address for each subnetwork in decimal format? Page 3 of 8

4 c. What is the broadcast address for each subnetwork in binary format? d. What is the subnet mask for each subnetwork in decimal format? e. How many addresses are expected to remain unused within each subnetwork? Page 4 of 8

5 Question 3 is based on the following network diagram. Subnet 1 Subnet A B C W X Y R a. What IP address should be configured as the default gateway of the hosts on Subnet 1? b. What is the purpose of this default gateway? c. i. What are gratuitous ARP requests and what are they used for? ii. What harm can they cause? d. Host W on Subnet 2 wants to send a packet to the host with IP address on Subnet 2. It needs to resolve the MAC address associated with the IP address of that host. i. What is the full name of the protocol used? ii. Give a detailed explanation of how this protocol works with specific reference to the network shown. [4] Page 5 of 8

6 Question 4 a. Several encoding methods are used in different communication applications. One such encoding scheme used is Differential Manchester encoding. i. What are the advantages and disadvantages of using this scheme? ii. Given that the signal below is generated using Differential Manchester Encoding which starts at low, what bit pattern does it represent? b. Another possible encoding scheme that may be used is the Non-Return to Zero Inverted or NRZI scheme. i. What are the advantages and disadvantages of using this scheme. ii. Draw the signal that would be generated using this scheme for the bit pattern Page 6 of 8

7 Question 5 is based on the diagrams shown below. The Transport layer uses two protocols. These are TCP and UDP. The following diagrams show the UDP header and TCP header respectively. UDP Header TCP Header a. What is TCP used for? b. What are the major characteristics of the TCP? c. What is UDP used for? Page 7 of 8

8 d. What are the major characteristics of the UDP? e. In the UDP header shown above, why are there no sequence numbers or window size fields as shown in the TCP header? f. i. What does it mean when we say that UDP is unreliable? ii. How is the fact that UDP is unreliable reflected in the header structure when compared to TCP? Question 6 a. Distance-vector routing protocols enjoy major benefits over link-state protocols. What are these benefits? b. Describe the updates sent out by Distance-vector routers? c. Link-state routing leads to faster convergence than distance-vector routing. i. What is convergence? ii. Why is convergence faster on link-state routing than distance-vector routing? d. Name and describe 5 types of metrics commonly used by routers. Question 7 a. Name and describe three different types of network attacks. b. An entry into an ACL is as follows: access-list 1 deny i. Will a packet from a machine with IP address be allowed? Explain. ii. What is the called and what is it used for? c. Besides network security, what is another reason to create ACLs? Page 8 of 8